Alexander wurts



(No Model.)

A. WURTS. SAFETY FUSE FOR ELECTRIC CIRCUITS. No. 434,168. Patented Aug. 12, 1890.

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A l w l G @iznesses v M W y A 4 I V UNITED STATES PATENT C FIcE.

ALEXANDER IVURTS, 0E PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THE IVESTINGIIOUSE ELECTRIC COMPANY, OF SAME PLACE.

SAFETY- FUSE FOR ELECTRIC CIRCUITS.

SPECIFICATION forming part of Letters Patent No. 434,168, dated August 12, 1890.

Application filed May 12, 1890. $erial No. 351,522. (No model.)

To all whom it may concern.-

Be it known that I, ALEXANDER WURTs, a citizen of the United States, residing in Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a certain new and useful Improvement in Safety-Fuses for Electric Circuits, (Case No. 40],) of which the following is a specification.

The invention relates to the class of appa ratus employed for protecting electric circuits and apparatus from the injurious effect of abnormal currents.

In operating certain classes of electrical apparatus under some circumstances currents of abnormal strength are liable to flow upon the circuits, and for the protection of the apparatus it is necessary that the circuits should be interrupted when such currents flow. In case the currents increase gradually the circuits may be protected by the use oflead or alloy fuses, which melt by reason of the heat developed in them on account of the resistance which they offer to the flow of current. In the event of a shortcircuit upon the generator, however, the current will increase in strength to such an extent as to form an are between the ends of the melted fuse, and it is then necessary that some means be employed for avoiding or im-' mediately interrupting this are in order to protect the machine and apparatus.

To this end the present invention consists.

in connecting in the circuit of an electric generator a lead or al1oyfusesuch as is commonly employed in electric circuits and adapted to protect the apparatus against abnormal currents within certain limitsand in series with this a second fuse responding only to currents of sufficient strength to form an are at the first fuse. This double set of fuses may be applied to each terminal of the generatoror side of the circuit, and they may be repeated at any portion of the circuit where necessary.

The accompanying drawing shows in diagram a system of circuits to which the devices are applied.

Referring to the drawing, A represents an electric generator of any suitable character, and L L main-line conductors leading therefrom to any suitable or desired work-circuit.

In series in the line I. there are placed two fuses B Z), and likewise two fuses B b are placed in series in the line L The fuse 13 consists of any usual form of lead or alloy fuses, such as are commonly employed for protecting electric circuits. In series with this the second fuse b is placed. This second fuse may be of thin iron or German-silver wire, of such crosssection, however, as to convey the normal currents to supply the work-circuit without undue heating and without offering great resistance to the flow of the current. The lead fuse B has a low meltingpoint and will protect the circuits and apparatus against the injurious effects due to most abnormal currents. The fuse Z) is required only when exceedingly high currents are flowing-such as would cause an are between the ends of the fuse B, which, being of a soft metal, is liable to volatilize, and the vapor affords a more or less perfect conducting medium. To such currents it will respond immediately. The length of the fuse b and its material is such as to prevent an are from forming between its ends. The fuses B and b are similar in construction and operation.

The fuses Z) b may be of other materials than iron or German silver, and likewise various different materials may be employed for constructing the fuses B B The fuse Z) might be employed alone and made to respond to all currents which will operate the fuse B; but a fuse having a high melting-point may be maintained at a dangerously-high temperature for a long time Without meltin The fuse l5, melting at a low temperature, is therefore employed for protecting the circuit from such currents as are not liable to form arcs. It should also be observed that the materials having low melting-pointssuch as it is necessary to employ in making the fuses B'conduce to the formation of arcs, while those employed for the fuse 17' do not easily are.

I claim as my invention 1. The combination of a lead or alloy fuse for'electric circuits having agiven meltingpoint, and a fuse of a higher melting-point,

connected in series therewith.

2. The combination, with an electric generator and its circuit, of a strip of fusible metal responding to currents of a given strength, and a second fuse connected in series therewith, responding only to a currentol' a greater strength.

3. The combination, with the poles of an electric generator, of a lead or alloy fuse and a fuse having a higher melting-point connected in series with each pole of the generator, substantially as described.

&. The combination, with the respective poles of an electric generator and its workcircuit, of a fuse having a given meltingpoint and a second fuse having a higher melting-point connected in series between each :5

the other being formed of German silver or 20 its equivalent.

In testimony whereof Ihave hereunto subscribed my name this 29th day of April,'A. D. 1890.

ALEXANDER WVURTS.

Witnesses:

FRANCIS PETTIT MANN, JAMES W. SMITH. 

